#00719B

CSS

:root {
  --chill-of-the-night: #00719b;
  --chill-of-the-night-rgb: 0 113 155;
  --chill-of-the-night-oklch: oklch(0.516 0.107 233.2);
}

.element {
  color: var(--chill-of-the-night);
  background-color: hsl(196 100% 30%);
  border-color: oklch(0.516 0.107 233.2);
}

Tailwind CSS v4

@theme {
  --color-chill-of-the-night: #00719b;
  --color-chill-of-the-night-50: #d9fbff;
  --color-chill-of-the-night-100: #c6eeff;
  --color-chill-of-the-night-200: #a8dcfc;
  --color-chill-of-the-night-300: #80c1e7;
  --color-chill-of-the-night-400: #57a9d3;
  --color-chill-of-the-night-500: #2491c1;
  --color-chill-of-the-night-600: #227ba3;
  --color-chill-of-the-night-700: #1c6283;
  --color-chill-of-the-night-800: #0f4961;
  --color-chill-of-the-night-900: #093244;
  --color-chill-of-the-night-950: #001e2c;
}

SCSS

$chill-of-the-night: #00719b;
$chill-of-the-night-rgb: 0, 113, 155;
$chill-of-the-night-light: mix(#fff, $chill-of-the-night, 20%);
$chill-of-the-night-dark: mix(#000, $chill-of-the-night, 20%);

.element {
  color: $chill-of-the-night;
  box-shadow: 0 0 0 2px rgba($chill-of-the-night, 0.35);
}